Low Guideline Compliance May Add to EVAR Risk

The majority of patients receiving endovascular repair for an aortic abdominal aneurysm failed to meet criteria for intervention as opposed to surveillance, and more than 58% of these patients failed to meet conservative criteria for device use based on manufacturer instructions, according to a large retrospective database study.

In addition, at 5 years post EVAR, 41% of the patients showed aneurysm sac enlargement, an outcome considered a surrogate for potential aneurysm rupture, according to a report.

This is an important issue because “in 2006, 21,725 EVAR procedures were performed in the United States, exceeding for the first time the number of open surgical AAA repairs,” according to Dr. Andres Schanzer of the University of Massachusetts, Worcester, and his colleagues at the Harvard School of Public Health, Boston, and the Cleveland Clinic Foundation.

In addition, although studies have demonstrated substantially lower morbidity and mortality after EVAR than after open repair, “late survival of these cohorts has demonstrated that the early survival advantage of patients undergoing EVAR disappears with time and a significant proportion of late deaths after EVAR are due to aneurysm rupture.”

Dr. Schanzer and his colleagues conducted a retrospective analysis of patients in M2S Inc.'s imaging database. M2S has served as the core imaging laboratory for several large aneurysm management trials and provides these services to both public and private academic hospitals globally. The study population consisted of 10,228 patients who underwent EVAR for AAA repair in 1999-2008, and who had a baseline CT scan before EVAR and at least one follow-up CT scan. The patients were primarily men (84.1%) with a mean age of 73.9 years, and represented all regions of the United States.

Key anatomical measurements included maximum AAA sac diameter, aortic diameter at the lowest renal artery, aortic neck length (distance between the lowest renal artery and the origin of the aneurysm, indicated by a 10% increase in diameter), aortic neck angulation (angle calculated between the lowest renal artery, the origin of the aneurysm, and the aortic bifurcation), conical neck (aortic diameter at 15 mm below the lowest renal artery greater than or equal to 10% larger than the aortic diameter at the lowest renal artery), AAA volume, maximum common iliac diameter, and length from the lowest renal artery to the aortic bifurcation. Data on the exact endovascular device used were not available, and there were no data available regarding secondary interventions (Circulation 2011 April 10 [doi:10.1161/CIRCULATIONAHA.110.014902]).

The instructions for use (IFU) for each approved device was reviewed, and these criteria were incorporated into three descriptive variables: conservative IFU (most restrictive), liberal IFU (least restrictive), and time-dependent IFU (reflecting the most liberal IFU at each time point during the study period).

The primary end point was AAA sac enlargement (defined as a growth of 5 mm or more in the AAA maximal diameter from before EVAR to any post-EVAR CT scan, based on Society for Vascular Surgery reporting standards). The secondary end point was endoleak (defined as the presence of contrast-opacified blood within the aneurysm sac and outside the endovascular stent graft).

The average preoperative AAA maximum diameter was 54.8 mm, with 6,075 patients (59%) having an AAA maximum diameter of less than 55 mm. The average neck diameter was 23.1 mm, with a mean length of 20.7 mm and a mean angle of 36.9 degrees. In addition, 11.9% were found to have at least one common iliac aneurysm greater than 20 mm in diameter.

When all patients were classified according to IFU criteria, 5,983 patients (58.5%) were outside compliance with the conservative IFU, 3,178 patients (31.1%) were outside the liberal IFU, and 4,507 patients (44.1%) were outside the time-dependent IFU.

Population characteristics changed over the 10-year study period. An increasing number of patients undergoing EVAR were 80 years of age or older; the maximum AAA diameter before EVAR did not significantly change over time, but the average diameter of the AAA neck did increase significantly; and significantly more patients undergoing EVAR had highly angulated aortic necks (7.0% in 1999-2003 vs. 9.5% in 2008) or conical aortic necks (30% vs. 35.7%). In addition, the external iliac diameter in patients decreased significantly over the study period, with 14.8% having both external iliac arteries measuring less than 6 mm in 1999-2003, compared with 17.5% in 2008. Mean follow-up was 31 months, with an average of three postoperative CT scans per patient. At 1, 3, and 5 years after EVAR, AAA sac enlargement was seen in 3%, 17%, and 41% of patients, respectively.

“The rate of AAA sac enlargement was significantly higher in patients who underwent EVAR outside the IFU, regardless of whether lack of compliance was on the basis of conservative IFU, liberal IFU, or time-dependent IFU,” the researchers stated. In addition, the rate of AAA sac enlargement was significantly greater in the group undergoing EVAR more recently (2004-2008), compared with the group who underwent EVAR in 1999-2003.

Multivariate analysis showed that the primary determinate of AAA sac enlargement was the presence of an endoleak on any postop CT scan (hazard ratio, 2.70). Additional significant predictors were a patient age of 80 years or older, an aortic neck diameter of 28 mm or larger, a neck angle greater than 60 degrees, and a common iliac artery diameter less than 20 mm.

Liberalization of the anatomical characteristics “deemed suitable for EVAR has occurred, and several of these factors, including aortic neck diameter, aortic neck angle, and common iliac artery diameter, were independently associated with aortic aneurysm sac enlargement. These observations raise the question as to whether such liberalization is justified with current device designs,” the authors suggested.

“In this multicenter patient population, compliance with published EVAR device IFU guidelines was low, and post-EVAR aneurysm sac enlargement was high, raising concern for long-term risk of aneurysm rupture,” the researchers stated. In addition, the liberalization in the anatomical criteria deemed appropriate for EVAR, observed throughout the study period, “was associated with worse outcomes.”

The authors suggested the need for a prospective EVAR registry incorporating an independent imaging registry to define more precisely the specific aortic and iliac artery anatomy suitable for EVAR with available commercial devices.

Although this is the largest investigation of this question to date, the authors noted several limitations to their study, beyond the lack of device identification and information on secondary interventions. They pointed out that current research indicates that the standard definition of maximum diameter growth of 5 mm or more may be a less-sensitive criterion for sac enlargement than are volume assessments.

Their study indicated a greater need for concern for proper patient selection for EVAR, they concluded.

An improved understanding of these anatomical characteristics “will ultimately improve the effectiveness and durability of EVAR to protect patients against AAA rupture,” Dr. Schanzer and his colleagues said.

The authors reported that they had no disclosures.

The majority of patients receiving endovascular repair for an aortic abdominal aneurysm failed to meet criteria for intervention as opposed to surveillance, and more than 58% of these patients failed to meet conservative criteria for device use based on manufacturer instructions, according to a large retrospective database study.

In addition, at 5 years post EVAR, 41% of the patients showed aneurysm sac enlargement, an outcome considered a surrogate for potential aneurysm rupture, according to a report.

This is an important issue because “in 2006, 21,725 EVAR procedures were performed in the United States, exceeding for the first time the number of open surgical AAA repairs,” according to Dr. Andres Schanzer of the University of Massachusetts, Worcester, and his colleagues at the Harvard School of Public Health, Boston, and the Cleveland Clinic Foundation.

In addition, although studies have demonstrated substantially lower morbidity and mortality after EVAR than after open repair, “late survival of these cohorts has demonstrated that the early survival advantage of patients undergoing EVAR disappears with time and a significant proportion of late deaths after EVAR are due to aneurysm rupture.”

Dr. Schanzer and his colleagues conducted a retrospective analysis of patients in M2S Inc.'s imaging database. M2S has served as the core imaging laboratory for several large aneurysm management trials and provides these services to both public and private academic hospitals globally. The study population consisted of 10,228 patients who underwent EVAR for AAA repair in 1999-2008, and who had a baseline CT scan before EVAR and at least one follow-up CT scan. The patients were primarily men (84.1%) with a mean age of 73.9 years, and represented all regions of the United States.

Key anatomical measurements included maximum AAA sac diameter, aortic diameter at the lowest renal artery, aortic neck length (distance between the lowest renal artery and the origin of the aneurysm, indicated by a 10% increase in diameter), aortic neck angulation (angle calculated between the lowest renal artery, the origin of the aneurysm, and the aortic bifurcation), conical neck (aortic diameter at 15 mm below the lowest renal artery greater than or equal to 10% larger than the aortic diameter at the lowest renal artery), AAA volume, maximum common iliac diameter, and length from the lowest renal artery to the aortic bifurcation. Data on the exact endovascular device used were not available, and there were no data available regarding secondary interventions (Circulation 2011 April 10 [doi:10.1161/CIRCULATIONAHA.110.014902]).

The instructions for use (IFU) for each approved device was reviewed, and these criteria were incorporated into three descriptive variables: conservative IFU (most restrictive), liberal IFU (least restrictive), and time-dependent IFU (reflecting the most liberal IFU at each time point during the study period).

The primary end point was AAA sac enlargement (defined as a growth of 5 mm or more in the AAA maximal diameter from before EVAR to any post-EVAR CT scan, based on Society for Vascular Surgery reporting standards). The secondary end point was endoleak (defined as the presence of contrast-opacified blood within the aneurysm sac and outside the endovascular stent graft).

The average preoperative AAA maximum diameter was 54.8 mm, with 6,075 patients (59%) having an AAA maximum diameter of less than 55 mm. The average neck diameter was 23.1 mm, with a mean length of 20.7 mm and a mean angle of 36.9 degrees. In addition, 11.9% were found to have at least one common iliac aneurysm greater than 20 mm in diameter.

When all patients were classified according to IFU criteria, 5,983 patients (58.5%) were outside compliance with the conservative IFU, 3,178 patients (31.1%) were outside the liberal IFU, and 4,507 patients (44.1%) were outside the time-dependent IFU.

Population characteristics changed over the 10-year study period. An increasing number of patients undergoing EVAR were 80 years of age or older; the maximum AAA diameter before EVAR did not significantly change over time, but the average diameter of the AAA neck did increase significantly; and significantly more patients undergoing EVAR had highly angulated aortic necks (7.0% in 1999-2003 vs. 9.5% in 2008) or conical aortic necks (30% vs. 35.7%). In addition, the external iliac diameter in patients decreased significantly over the study period, with 14.8% having both external iliac arteries measuring less than 6 mm in 1999-2003, compared with 17.5% in 2008. Mean follow-up was 31 months, with an average of three postoperative CT scans per patient. At 1, 3, and 5 years after EVAR, AAA sac enlargement was seen in 3%, 17%, and 41% of patients, respectively.

“The rate of AAA sac enlargement was significantly higher in patients who underwent EVAR outside the IFU, regardless of whether lack of compliance was on the basis of conservative IFU, liberal IFU, or time-dependent IFU,” the researchers stated. In addition, the rate of AAA sac enlargement was significantly greater in the group undergoing EVAR more recently (2004-2008), compared with the group who underwent EVAR in 1999-2003.

Multivariate analysis showed that the primary determinate of AAA sac enlargement was the presence of an endoleak on any postop CT scan (hazard ratio, 2.70). Additional significant predictors were a patient age of 80 years or older, an aortic neck diameter of 28 mm or larger, a neck angle greater than 60 degrees, and a common iliac artery diameter less than 20 mm.

Liberalization of the anatomical characteristics “deemed suitable for EVAR has occurred, and several of these factors, including aortic neck diameter, aortic neck angle, and common iliac artery diameter, were independently associated with aortic aneurysm sac enlargement. These observations raise the question as to whether such liberalization is justified with current device designs,” the authors suggested.

“In this multicenter patient population, compliance with published EVAR device IFU guidelines was low, and post-EVAR aneurysm sac enlargement was high, raising concern for long-term risk of aneurysm rupture,” the researchers stated. In addition, the liberalization in the anatomical criteria deemed appropriate for EVAR, observed throughout the study period, “was associated with worse outcomes.”

The authors suggested the need for a prospective EVAR registry incorporating an independent imaging registry to define more precisely the specific aortic and iliac artery anatomy suitable for EVAR with available commercial devices.

Although this is the largest investigation of this question to date, the authors noted several limitations to their study, beyond the lack of device identification and information on secondary interventions. They pointed out that current research indicates that the standard definition of maximum diameter growth of 5 mm or more may be a less-sensitive criterion for sac enlargement than are volume assessments.

Their study indicated a greater need for concern for proper patient selection for EVAR, they concluded.

An improved understanding of these anatomical characteristics “will ultimately improve the effectiveness and durability of EVAR to protect patients against AAA rupture,” Dr. Schanzer and his colleagues said.

The authors reported that they had no disclosures.

The majority of patients receiving endovascular repair for an aortic abdominal aneurysm failed to meet criteria for intervention as opposed to surveillance, and more than 58% of these patients failed to meet conservative criteria for device use based on manufacturer instructions, according to a large retrospective database study.

In addition, at 5 years post EVAR, 41% of the patients showed aneurysm sac enlargement, an outcome considered a surrogate for potential aneurysm rupture, according to a report.

This is an important issue because “in 2006, 21,725 EVAR procedures were performed in the United States, exceeding for the first time the number of open surgical AAA repairs,” according to Dr. Andres Schanzer of the University of Massachusetts, Worcester, and his colleagues at the Harvard School of Public Health, Boston, and the Cleveland Clinic Foundation.

In addition, although studies have demonstrated substantially lower morbidity and mortality after EVAR than after open repair, “late survival of these cohorts has demonstrated that the early survival advantage of patients undergoing EVAR disappears with time and a significant proportion of late deaths after EVAR are due to aneurysm rupture.”

Dr. Schanzer and his colleagues conducted a retrospective analysis of patients in M2S Inc.'s imaging database. M2S has served as the core imaging laboratory for several large aneurysm management trials and provides these services to both public and private academic hospitals globally. The study population consisted of 10,228 patients who underwent EVAR for AAA repair in 1999-2008, and who had a baseline CT scan before EVAR and at least one follow-up CT scan. The patients were primarily men (84.1%) with a mean age of 73.9 years, and represented all regions of the United States.

Key anatomical measurements included maximum AAA sac diameter, aortic diameter at the lowest renal artery, aortic neck length (distance between the lowest renal artery and the origin of the aneurysm, indicated by a 10% increase in diameter), aortic neck angulation (angle calculated between the lowest renal artery, the origin of the aneurysm, and the aortic bifurcation), conical neck (aortic diameter at 15 mm below the lowest renal artery greater than or equal to 10% larger than the aortic diameter at the lowest renal artery), AAA volume, maximum common iliac diameter, and length from the lowest renal artery to the aortic bifurcation. Data on the exact endovascular device used were not available, and there were no data available regarding secondary interventions (Circulation 2011 April 10 [doi:10.1161/CIRCULATIONAHA.110.014902]).

The instructions for use (IFU) for each approved device was reviewed, and these criteria were incorporated into three descriptive variables: conservative IFU (most restrictive), liberal IFU (least restrictive), and time-dependent IFU (reflecting the most liberal IFU at each time point during the study period).

The primary end point was AAA sac enlargement (defined as a growth of 5 mm or more in the AAA maximal diameter from before EVAR to any post-EVAR CT scan, based on Society for Vascular Surgery reporting standards). The secondary end point was endoleak (defined as the presence of contrast-opacified blood within the aneurysm sac and outside the endovascular stent graft).

The average preoperative AAA maximum diameter was 54.8 mm, with 6,075 patients (59%) having an AAA maximum diameter of less than 55 mm. The average neck diameter was 23.1 mm, with a mean length of 20.7 mm and a mean angle of 36.9 degrees. In addition, 11.9% were found to have at least one common iliac aneurysm greater than 20 mm in diameter.

When all patients were classified according to IFU criteria, 5,983 patients (58.5%) were outside compliance with the conservative IFU, 3,178 patients (31.1%) were outside the liberal IFU, and 4,507 patients (44.1%) were outside the time-dependent IFU.

Population characteristics changed over the 10-year study period. An increasing number of patients undergoing EVAR were 80 years of age or older; the maximum AAA diameter before EVAR did not significantly change over time, but the average diameter of the AAA neck did increase significantly; and significantly more patients undergoing EVAR had highly angulated aortic necks (7.0% in 1999-2003 vs. 9.5% in 2008) or conical aortic necks (30% vs. 35.7%). In addition, the external iliac diameter in patients decreased significantly over the study period, with 14.8% having both external iliac arteries measuring less than 6 mm in 1999-2003, compared with 17.5% in 2008. Mean follow-up was 31 months, with an average of three postoperative CT scans per patient. At 1, 3, and 5 years after EVAR, AAA sac enlargement was seen in 3%, 17%, and 41% of patients, respectively.

“The rate of AAA sac enlargement was significantly higher in patients who underwent EVAR outside the IFU, regardless of whether lack of compliance was on the basis of conservative IFU, liberal IFU, or time-dependent IFU,” the researchers stated. In addition, the rate of AAA sac enlargement was significantly greater in the group undergoing EVAR more recently (2004-2008), compared with the group who underwent EVAR in 1999-2003.

Multivariate analysis showed that the primary determinate of AAA sac enlargement was the presence of an endoleak on any postop CT scan (hazard ratio, 2.70). Additional significant predictors were a patient age of 80 years or older, an aortic neck diameter of 28 mm or larger, a neck angle greater than 60 degrees, and a common iliac artery diameter less than 20 mm.

Liberalization of the anatomical characteristics “deemed suitable for EVAR has occurred, and several of these factors, including aortic neck diameter, aortic neck angle, and common iliac artery diameter, were independently associated with aortic aneurysm sac enlargement. These observations raise the question as to whether such liberalization is justified with current device designs,” the authors suggested.

“In this multicenter patient population, compliance with published EVAR device IFU guidelines was low, and post-EVAR aneurysm sac enlargement was high, raising concern for long-term risk of aneurysm rupture,” the researchers stated. In addition, the liberalization in the anatomical criteria deemed appropriate for EVAR, observed throughout the study period, “was associated with worse outcomes.”

The authors suggested the need for a prospective EVAR registry incorporating an independent imaging registry to define more precisely the specific aortic and iliac artery anatomy suitable for EVAR with available commercial devices.

Although this is the largest investigation of this question to date, the authors noted several limitations to their study, beyond the lack of device identification and information on secondary interventions. They pointed out that current research indicates that the standard definition of maximum diameter growth of 5 mm or more may be a less-sensitive criterion for sac enlargement than are volume assessments.

Their study indicated a greater need for concern for proper patient selection for EVAR, they concluded.

An improved understanding of these anatomical characteristics “will ultimately improve the effectiveness and durability of EVAR to protect patients against AAA rupture,” Dr. Schanzer and his colleagues said.

The authors reported that they had no disclosures.